<template>
  <!--分页器-->
  <div class="pagination">
    <button :disabled="pageNo==1" @click="$emit('getpageNo',pageNo-1)">上一页</button>
    <button v-if="startAndEndNum.start>1" @click="$emit('getpageNo',1)" :class="{active:pageNo==1}">1</button>
    <button v-if="startAndEndNum.start>2">...</button>

    <button v-for="(page,index) in startAndEndNum.end" :key="index" v-show="page>=startAndEndNum.start"
            @click="$emit('getpageNo',page)" :class="{active:pageNo==page}">{{ page }}
    </button>

    <button v-if="startAndEndNum.end<totalPage-1">···</button>
    <button v-if="startAndEndNum.end<totalPage" @click="$emit('getpageNo',totalPage)"
            :class="{active:pageNo==totalPage}">{{ totalPage }}
    </button>
    <button :disabled="pageNo==totalPage" @click="$emit('getpageNo',pageNo+1)">下一页</button>
    <button style="margin-left: 20px">共{{ total }}条</button>
  </div>
</template>

<script>
export default {
  name: "pagination",
  // pageNo：当前页码；   pageSize：每页条数；   total:数据总条数；    continues：显示页码的个数（页码规格）
  props: ['pageNo', 'pageSize', 'total', 'continues'],
  computed: {
    // 共多少页
    totalPage() {
      // 向上取整
      return Math.ceil(this.total / this.pageSize)
    },

    startAndEndNum() {
      const {pageNo, totalPage, continues} = this
      let start = 0, end = 0
      if (continues > totalPage) {
        start = 1, end = totalPage
      } else {
        start = pageNo - parseInt(continues / 2)
        end = pageNo + parseInt(continues / 2)
        if (start < 1) {
          start = 1
          end = continues
        }
        if (end > totalPage) {
          end = totalPage
          start = totalPage - continues + 1
        }
      }
      return {start, end}
    }
  }
}
</script>

<style scoped lang="less">
.pagination {
  text-align: center;

  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {

      // 只能点击一次
      cursor: not-allowed;
      background-color: #ea4a36;
      color: #fff;
    }
  }
}
</style>